This invention relates to a method of forming an insoluble coating on a substrate from an unhydrolyzed silane. The method generally comprises applying a coating mixture comprising the silane and, optionally, a titanium catalyst on the substrate and allowing the coating mixture to hydrolyze in atmospheric moisture and condense to form the insoluble coating.
It is known in the art that hydrolyzed or partially hydrolyzed silanes are useful for forming coatings. For instance, Levene in U.S. Pat. No. 3,811,918 teaches the use of partially hydrolyzed silicon alkoxides and metal oxide forming compounds to form protective coatings. Similarly, Collins et al. in U.S. Pat. No. 3,615,272 and Haluska et al. in U.S. Pat. No. 4,756,977 teach the use of hydrolyzed trichlorosilane (i.e., hydrogen silsesquioxane resin) to form coatings on substrates. Finally, Haluska et al. in U.S. Pat. No. 4,753,856 teach the use of hydrogen silsesquioxane resin with metal oxide precursors (including titanium oxide) for forming coatings on substrates.
Such processes are disadvantageous in many instances because they require the silane be hydrolyzed prior to forming the coatings. This hydrolysis can be costly, time consuming and can generate a variety of undesirable by-products. It has now been unexpectedly found that coatings of siloxane resin or silicate structure can be formed by in-place hydrolysis and condensation of surface films of silanes.